The presently disclosed embodiments relate generally to agitation devices and methods for the making of wine.
In the fermentation of red wine, carbon dioxide gas is generated, and this causes the grape skins present in the fermentation to float up to the top of the liquid in the fermenter and form what is termed a “cap.” During fermentation, this cap must be periodically broken up so that the skins are mixed into the liquid in order to most effectively extract color and flavor compounds from the skins and seeds. The cap must also be kept moist to prevent the growth of deleterious aerobic bacteria.
Conventionally, the agitation of the cap is performed by poking the cap with a pole to break it up. This tedious process is termed “punch down” and must be performed several times a day. Conventional punchdown techniques require an open top fermentation vessel. These open top fermenters permit air to contact the fermenting wine causing unwanted oxidation.
Although automated punchdown devices are commercially available, such devices are both mechanically complex, and require a moving seal to prevent contaminating the fermenting wine. Alternatively, other conventional methods for performing automated punchdown include pumping the liquid taken from the bottom of the fermenter over the cap to moisten it; however, although this conventional technique is widely used, it is ineffective in breaking up the cap.
Other techniques for “cap management” include using horizontally rotating fermenters (Rieger, U.S. Pat. No. 4,474,890 and Speidel, EP 0337060) that force the cap into the liquid. Such devices, however, are expensive and complex machines with large rotating assemblies, making them impractical for most wineries. Klein et. al. (U.S. Pat. No. 6,703,055) describes a fermentation tank with rotating mechanical agitators to flood the cap when needed.